Attachment of hair-springs to balance-staffs



(No Model.)

J. M. HEARD. Attachment of Hair Springs to Balance Staff.

No. 228,995. Patented June 22,1880.

mmxma Masses.

' UNITED STATES PATENT OFFICE.

JAMES M. HEARD, OF ST. PAUL, MINNESOTA.

ATTACHMENT OF HAIR-SPRINGS TO BALANCE-STAFFS.

SPECIFICATION forming part of Letters Patent No. 228,995, dated June 22,1880.

Application filed April 5, 1880. (No model.)

To all whom it may concern:

Be it known that I, JAMES MIL'roN HEARD, of St. Paul, in the county ofRamsey and State of Minnesota, have invented a new and usefulImprovement in the Method of Attaching the Hair-Springs to the Staffs inWatches, &c., of which the following is a specification.

This invention relates to the hair-sprin gs of watches, 850.; and itconsists in so securing the inner end of the spring to the staff thatthe point of commencement of the vibration will occur at a point at orbetween the center and periphery of the staff, whereby all parts of theouter coil will be isochronal, as hereinafter set forth.

I attain these results by the mechanism i1- lustrated in theaccompanying drawings, in which Figure l is a plan view, and Fig. 2 is asectional side elevation, of a com pensatin gwheel, hair-spring, andstaff of a watch enlarged five diameters, showing the method of applyingmy invention. Fig. 3 is a cross-section, and Fig. 4 a side elevation, ofa portion of the staff and hair-spring enlarged fifteen times, showingmy manner of securing the spring to the staff; Figs. 5 and 6, similarviews, illust 'ating the ordinary method of securing the spring.

A is the compensating-wheel, B the staff, and O the hair-spring, allmade in the usual manner.

In the ordinary method of securing the spring to the staff its inner endis passed through a hole through the side of a collet, a, (see Figs. 5and 6,) on the staff and fastened therein by a wedge, I), while theouter end is secured to the under side of the cock at its isochronalpoint. In this method the isochronal point ordinarily occurs on theouter coil at or near the part c, Fig. 1, but not always so, as thispoint is very uncertain by reason of the varying thickness, length, andtemper of the springs. Great care, nicety of adjustment, and experimentare necessary to determine its exact location.

If the spring were so attached to the staff that the exact center of thecoil would be in the exact center of the staff, all points on the outercoil would be isochronal, and this advantage I obtain by securing thesprin 0 directly to the staff B by passing its inner end through a hole,(I, drilled through the staff, and fastening it" therein by a wedge, c.This brings the point 1 of the commencement of the vibration of thespring very near the center of the staff, while in the ordinary mannerof fastening itby the collct this point occurs at the periphery of thelatter, as shown in Figs. 5 and 6.

By my arrangement the center of the coil will be brought so near thecenter of the staff that all parts of the outer coil will beapproximately isochronal; but by countersinking the side of the hole (1next the vibration-point 9 this vibration-point will be brought backexactly to the center, so that all parts of the outer coil will berendered still nearer isochronal, or at least near enough for allpractical purposes, this isochronism being a matter of such delicateadjustment that it is next to an utter impossibility to perfectly attainit; but by my arrangement of the vibration-point exactly in the centerof the staff I claim that, other things being equal, all watches may bemade practically isochronous. This is a very important improvement, asby the old method it is a matter of great difficulty and expense to findthe isochronal point of the spring; but by my arrangement all parts ofthe outer coil are isochronal; hence perfect time is insured.

What I claim as new is A watch balance-staff having a hole through thecenter of its upper part at right angles to its axial line, in which theinner end of the hair-spring is secured, whereby the point ofcommencement of the vibration of the spring occurs at apoint at thecenter of the staff, or at a point between the center and periphery,

substantially as set forth.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

JAMES MILTON HEARD.

Witnesses S. S. WOLCOTT, G. N. WOODWARD.

